A gentle breeze blows across the harbor of San Cristóbal, the easternmost island in the Galápagos archipelago. Sea lions bask on the beach under the equatorial sun, and blue-footed boobies dive for anchovies in the Pacific waters. A round brown finch swoops down from a prickly-pear cactus, flutters in midair for an instant, and then lands on my head.

Tens of thousands of tourists come to the Galápagos Islands each year to get close to its extraordinary fauna—to snorkel with hammerhead sharks, hang out with giant tortoises, and have their scalps inspected by Darwin’s finches. The archipelago’s exquisitely unique creatures gave Charles Darwin a good deal of inspiration for his theory of evolution when he visited in 1835. Nature-loving visitors now flock to the islands in hopes of seeing what Darwin saw.

Ironically, the influx of ecominded tourists now threatens this island paradise. In particular, the huge demand for electricity to power hotels, shops, and restaurants, as well as the homes of permanent residents, has placed an enormous burden on the islands’ power grid, which until recently relied entirely on diesel generators. In 2007, about 5 million liters of diesel fuel had to be shipped in from the mainland to keep the generators running, and demand is growing 10 ­percent each year.

Seven years ago, after a tanker ran aground and spilled more than half a million liters of fuel into San Cristóbal’s harbor, the government of Ecuador, which governs the islands, intensified efforts to free the Galápagos from fossil fuels. A like-minded group of United Nations officials, power engineers, and government representatives came together to devise an energy scheme for the islands, based on renewable energy.

To realize their goal, they had to overcome unexpected technical and logistical hurdles, ease environmental concerns about their project’s potential impact on the fragile ecosystem, and cut through the inevitable bureaucratic red tape. There were moments when even the project’s leaders feared it would never happen. But this past fall, the team finally installed three enormous wind turbines in the San Cristóbal hills, capable of supplying half the island’s electricity.

”This is one of the biggest wind-diesel hybrid projects in the world,” says Luis Vintimilla, an Ecuadorian engineer and one of the project managers. ”We hope it will be a model for other islands in the Galápagos and elsewhere.”

Photos: From Left: Thomas R. Fletcher/Alamy; Reinhard Dirscherl/Alamy; David Hosking/Alamy; Gary Cralle/Getty Images; Stuart Gregory/Getty Images; Jacques Descloitres/MODIS Land Rapid Response Team/NASA/GSFC